Mullerian Inhibiting Substance (MIS) is a biological modifier developed in our laboratory for use in the treatment of tumors of Mullerian duct origin, namely ovarian, endometrial, and cervical carcinomas, all of which express MIS type II receptors (MISRII) and respond to MIS in growth inhibitory assays. MIS was recently found to be equally effective against breast and prostate cancers. However, the focus in this grant is on ovarian cancer because of its lethality and the lack of a therapeutic regimen capable of providing long term benefit to a high percentage of patients. MIS and its receptors have been cloned and multiple sources have been explored for the production of recombinant human (rh)MIS, including E.coli, yeast, baculovirus, mammalian cells, plants, and milk. The rhMIS with the best yield, reproducible biologic activity and efficacy against tumors, and the least contamination, thus far, is produced in mammalian cells and isolated from serum free media. A specific MIS ELISA has been developed to follow its production and pharmacokinetics, and antibodies developed to MIS receptors make it possible to preselect patients who may respond to MIS. 1) MIS will be produced in transfected mammalian cells and purified from serum free media using methods which adhere to FDA standards for human use. 2) The formulation produced will be tested against ovarian carcinoma cell lines in vivo and in vitro, alone, and in combination first with doxorubicin, which shows synergy with MIS and later, with other cytotoxic drugs. RhMIS pharmacokinetics will be studied in mice in order to design future treatment schedules. 3) MIS-C alone and in combination with its receptors will be cocrystallized for structure function studies to guide future rational drug design. The inhibitory effect of rhMIS in vivo against ovarian carcinomas is compelling. These experiments will pave the way for use of MIS in the clinic and will define a source for scale up to meet FDA standards.